A sample of methane gas, CH4 was collected over water at 25 degrees celcius and 720 torr. The volume of the wet gas is 2.50L. What will be the volume of the dry methane at a standard pressure?

I would use

(P1V1/T1) = (P2V2/T2)and solve for V2.
For P1, use 720 torr minus vapor pressure H2O at 25 degrees C. You can find that in tables; it varies with T and is approximately 25 torr at 25 C but you need to use the value in the table.

To determine the volume of the dry methane at a standard pressure, we need to first calculate the pressure of the dry methane. We can use Dalton's Law of Partial Pressure to find this.

Dalton's Law states that the total pressure of a gas mixture is equal to the sum of the partial pressures of each gas in the mixture. In this case, the total pressure is equal to the pressure of the collected gas (720 torr) plus the vapor pressure of water at the given temperature (25 degrees Celsius).

To convert the temperature to Kelvin, we add 273.15 to the Celsius temperature:
25 degrees Celsius + 273.15 = 298.15 Kelvin

Next, we need to find the vapor pressure of water at 25 degrees Celsius. We can look up this value in a reference table or search online. The vapor pressure of water at 25 degrees Celsius is approximately 23.76 torr.

Now, we can calculate the pressure of the dry methane:
Pressure of dry methane = Total pressure - Vapor pressure of water
Pressure of dry methane = 720 torr - 23.76 torr = 696.24 torr

Finally, to find the volume of the dry methane at standard pressure, we can use Boyle's Law, which states that the volume of a gas is inversely proportional to its pressure, assuming temperature and moles of gas remain constant.

Boyle's Law equation: P1V1 = P2V2

In this case, we know the initial pressure (696.24 torr), the initial volume (2.50 liters), and we want to find the final volume at standard pressure (1 atmosphere or 760 torr).

Using the equation, we can solve for V2 (the final volume):
V2 = (P1 * V1) / P2
V2 = (696.24 torr * 2.50 L) / 760 torr
V2 ≈ 2.29 L

Therefore, the volume of the dry methane at standard pressure (1 atm) would be approximately 2.29 L.

To find the volume of the dry methane at standard pressure, we need to use the Ideal Gas Law equation, which is:

PV = nRT

Where:
P = Pressure
V = Volume
n = Number of moles
R = Gas constant
T = Temperature

First, we need to find the number of moles of methane gas. To do that, we'll use the equation:

n = PV/RT

Given:
P = 720 torr
V = 2.50 L
R = 0.0821 L·atm/(mol·K)
T = 25 degrees Celsius = 25 + 273.15 = 298.15 K

Now we can calculate the number of moles:

n = (720 torr * 2.50 L) / (0.0821 L·atm/(mol·K) * 298.15 K)
n = 60.48 torr·L / (0.0821 L·atm/(mol·K) * 298.15 K)
n ≈ 2.019 mol

Since the number of moles remains the same when the gas is dried, we'll use this value to find the volume of the dry methane at standard pressure.

At standard pressure, the pressure is 1 atm, and since we're only interested in volume, we can rearrange the Ideal Gas Law equation to solve for V:

V = nRT/P

Given:
n = 2.019 mol
R = 0.0821 L·atm/(mol·K)
P = 1 atm

Now we can calculate the volume of the dry methane at standard pressure:

V = (2.019 mol * 0.0821 L·atm/(mol·K) * 298.15 K) / 1 atm
V ≈ 49.58 L

Therefore, the volume of the dry methane at standard pressure is approximately 49.58 L.